1. Field of the Invention
The present invention generally relates to radiation imaging, and more particularly it relates to a multi-radiation unit and a radiation imaging system using the unit. These can be applicable to radiation imaging for medical diagnosis or non-destructive inspection in the fields of medical and industrial equipment.
2. Description of Related Art
A radiation tube generally accelerates electrons emitted from an electron source to have high energy to form an electron beam having a desired shape, and then a target is irradiated with the electron beam to generate radiation from the target.
Japanese Patent Application Laid-Open No. 2007-265981 discloses a multi-radiation tube in which a plurality of electron sources are arranged to face a plurality of targets, respectively so that a plurality of radiations are generated.
The radiations generated in the multi-radiation tube have their respective intensity distributions, and each of the intensity distributions depends on the size of the focal point of the corresponding radiation. The size of the focal point of each radiation depends on the characteristic of the corresponding electron source. If the electron sources have different characteristics, the respective radiations emitted from the electron sources have different intensity distributions. Therefore, if such a multi-radiation tube is used for a radiation imaging system, for example, the quality of an entire image, such contrast of a captured image, is degraded.